The present invention relates to a fundamental unit of processing a video signal in the form of raster scanning and more particularly to a fundamental unit for processing a video signal continuously in real time without any interruption.
One of the examples of a video signal obtained by raster scanning is a television signal. It is well known in the art that various processings of a television signal include processings on an amplitude axis, on a frequency axis and on a time axis and geometrical transformation of a picture.
So far, in order to effect such various processings, specific circuits and devices for accomplishing specific functions have been used. For instance, to provide correction of the time axis, a time base corrector and a frame synchronizer have been used and in a case of geometrical transformation, a digital video effector or the like has been used.
These circuits and devices, however, only have respectively specified functions and consequently cannot readily be applied for other purposes and cannot readily be expanded to accomplish other functions.
In order to explain in more detail prior art circuits and devices of the types described above, one example of a conventional program production system is shown in FIG. 1. In FIG. 1, the outputs from TV cameras A and B are provided to a switcher 102 directly and through an image quality correction circuit 101. Video signals other than NTSC signal are applied through a system conversion unit 103 to the switcher 102. A video signal which is not synchronized and transmitted from another station is applied through a frame synchronizer 104 to the switcher 102. A video signal which has been suitably selected by the switcher 102 is applied through a mixing/effect amplifier 105 to a digital video effector (DVE) 106 so that a desired synthesized picture output is derived from the DVE 106.
However, the system as shown in FIG. 1 has the following problems.
(1) When a new function is needed, a specific circuit or device capable of accomplishing such function must be designed and fabricated additionally.
(2) In the system as shown in FIG. 1, when the insertion positions of, for example, the frame synchronizer 104, the image quality correction circuit 101 or the digital video effector 106 must be changed, it is necessary to change the wiring system.
(3) Novel special effects are demanded one after another, so that hardware capable of accomplishing such special effects must be fabricated, even when the frequency of use of such special effects is very small.
(4) A specific design idea must be employed in designing and fabricating a program production system depending upon whether the program production system is used specifically for relay broadcasting, or for broadcasting a program made in a studio, or news broadcasting. As a result, the program production system becomes very expensive.
As described above, a conventional program production system cannot be expanded and does not have versatility. In addition, a conventional program production system is not economical. Furthermore, even though various program production methods are employed at present, a conventional program production system is not adapted flexibly to satisfy such demands.
A digital computer capable of accomplishing desired processings by means of programmable logic circuits is known. Since the sampling cycle of a digital video signal is generally several tens of nano seconds, a ultra-high-speed computer is needed in order to accomplish such complicated processings of respective picture elements in the manner described above. As a result, a programable production system employing such digital processing becomes large-scale and very expensive.